This 21mm f/2.8 lens achieves its best DxOMark Score at f/2.8. If its resolution is not as high as many other Zeiss lenses, it remains solid both on full-frame and on APS-C sensors. Its most noticeable advantages are, here again, rather limited distortion for a wide angle lens, and very few chromatic aberrations. As with many wide angle lenses, this 21mm proves a solid companion for landscape both on APS-C and 24x36 sensors, and can also be used for reportage when mounted on an APS-C body.

On a full-frame sensor (EOS 1Ds MkIII):

On a full-frame sensor the resolution map is very sharp from the center to the first one-third, even fully opened. Stopping down to f/4 makes the same center to one-third of field even crisper; but as soon one reaches f/5.6, even if the center remains crisp, the last third and the corners become very soft. The best aperture range for this lens is definitely located between f/2.8 and f/4. Vignetting is quite pronounced at wide apertures, but at f/5.6 and onwards it becomes almost anecdotic.

On an APS-C sensor (EOS 7D)

The behavior of this 21mm mounted on an APS-C body is almost identical with its behavior on a full-frame, as far as definition is concerned. The center is correct fully opened. Stopping down to f/5.6 will produce a very sharp zone on two-third of the map, but the last one-third and the corners always remain much softer. Closing to f/8 and smaller reduces the size of the central sharp area. Here the best aperture range is located between f/4 (where the map is the the most regular) and f/5.6.If vignetting is visible at f/2.8, it vanishes two steps further. As soons as one reaches f/5.6, the map in perfect.

Further readings for the Latest results for Zeiss lenses

To provide photographers with a broader perspective about mobiles, lenses and cameras, here are links to articles, reviews, and analyses of photographic equipment produced by DxOMark, renown websites, magazines or blogs.

Carl Zeiss is one of those almost mythical lens makers. Focusing on quality, its lenses almost always rely on complex optical formulas. Their price reflects this involvement in quality, and logically Zeiss lenses are on the same shelves as the very high-end Canon or Nikon models. We have tested 14 of them so far, ranging from the ultra-wide-angle Distagon T18mm f/3.5 to the much heavier Makro Planar T100mm f/2.